Claude 4.0 Sonnet Merge Commit Message Generation rollout plan

What does this MR do and why?

Anthropic has released their new Sonnet 4.0 model. We need to upgrade all existing Sonnet integrations across GitLab Duo features. In this issue, we upgrade the model for Merge_Commit_Message_Generation

reference !183311 (merged) and gitlab-org/modelops/applied-ml/code-suggestions/ai-assist!2078 (merged)

issue: #545695 (closed)

this should be reviewed together with gitlab-org/modelops/applied-ml/code-suggestions/ai-assist!2708 (merged)

rollout issue: #548149 (closed)

References

Screenshots or screen recordings

Before	After

[4] pry(main)> Feature.enabled?(:generate_commit_message_claude_4_0)
=> true

2. go a merge request and generate a commit message

3. check AIGW logs and find Claude 4.0 Generate Commit Message

2025-06-06 12:45:52 [info     ] Returning prompt from the registry correlation_id=01JX324X5CSEGBAAB0502XP38P prompt_id=generate_commit_message/base prompt_name='Claude 4.0 Generate Commit Message' prompt_version=1.2.0

How to set up and validate locally

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #545695 (closed)